Fuel heating apparatus



April 11, 1944. J. D. PULLIAM 2,346,506

FUEL HEATING APPARATUS Filed Feb. 1, 1943 James ZLRuZZc'am, a? ,4 W

Patented Apr. 11, 1944 FUEL HEATING APPARATUS .iames D. Pulliam, SanAntonio, Tex., assignor of five per cent to Donald R. Parker; five percent to R. W. Barnes; ten per cent to Augustus McCloskey and A. T.Stevens (jointly), and forty per cent to N. A. Saigh ApplicationFebruary 1, 1943, Serial No. 474,355

*7 Claims.

to the injector nozzles associated with the engine cylinder, to heat thefuel in the lines to a temperature below the vaporization point of thefuel at the pressure maintained therein, to the end that highly heatedliquid fuel is sprayed under high pressure into the highly compressedair in the engine cylinders, thereby greatly facilitating the ignitionof the fuel under the heat and pressure generated in the cylinders. Theinvention is predicated upon the discovery that starting of a Dieselengine, particularly when the engine is cold, may be greatly facilitatedby preheating the fuel before its injection into the engine cylinders,

It is well understood by persons familiar with Diesel engines that thefuel is ignited when it is injected in the form of a fine spray into thehighly compressed air in the cylinder, because the air has been heatedto the ignition point of the oil, as a result of its high compression bythe engine piston. Theoretically, the compression of the air in thecylinders should raise its temperature well above the flash point of thefuel, but in practice, particularly when the weather is cold and thecylinder walls, pistons and the fuel are cold, this temperature is notimmediately reached and difficulty in starting is often encountered. Ofcourse, after the engine has been running for a short time, the partsbecome sufficiently heated to maintain efiicient operation.

The present invention is predicated upon the discovery that the startingof a cold engine under the above circumstances may be effectedsubstantially instantaneously by raising the temerature of the fuel inthe fuel lines leading to the injectors, so that highly heated liquidfuel is injected into the compressed air in the cylinders, since theheat of that although some times insufiicient to ignite cold fuel oil,is entirely adequate to ignite the heated oil.

The present invention provides novel means for heating the oil in thefuel lines prior to its injection into the engine cylinders. Theinvention must be distinguished from attempts heretofore made tofacilitate vaporization of liquid fuel by heating the fuel, prior to themixing of the fuel vapors with air, for instance, in a carburetor orother device for mixing gaseous fuel and air prior to its introductioninto the engine cylinders, since the fuel in accordance with the presentinvention is not vaporized in the line, but, on the contrary, isinjected in the form of a highly heated liquid spray into the cylinder.In other words, the fuel, under the pressure maintained in the fuel linebetween the pump and the injector, remains in liquid form, asdistinguished from gaseous form. Hence, a primary object of the presentinvention is to provide, in combination with a Diesel engine, means forfacilitating starting of the engine, particularly when cold, by raisingthe temperature of the liquid fuel, substantially to the flash point,before it is injected under high pressure into the compressed air in thecylinders of the engine.

Another object of the invention is to heat the fuel in the fuel linesbetween the fuel pump and the injector nozzles or assemblies, so thatcompression ignition of the injected fuel is greatly facilitated,particularly when the engine is cold.

A further object of the invention is to heat the fuel in the fuel linesto a temperature below the vaporization temperature of the fuel at thepressure maintained in the lines between the pump and the injectors tothe end that the ignition of the liquid fuel injected into the air inthe cylinders, heated by the compression thereof, is positively assured,

A further object of the invention is to provide a device of thischaracter which may be employed for starting and which may readily berendered inoperative when the engine has become warmed up, by operationfor a short time.

A further object of the invention is to provide a device adapted toperform these fuctions which is characterized-by extreme simplicity, lowcost of manufacture, substantial absence of critical materials and easeof attachment to existing engines or to newly produced engines.

Another object is to provide a heating device of this character havingnovel details of construction, adapted to conserve heat, to preventexternal radiation and loss of heat and to concentrate the heat upon thefuel pipe and the fuel therein, preferably immediately ahead of theinjector assembly.

Other and further objects and advantages of the invention will beapparent to those skilled in the art, from a consideration of thefollowing description of a specific embodiment of th invention,described below and shown in the accompanying drawing, in which:

Figure l is a somewhat diagrammatic side elevation of a Diesel engineshowing the devices of the present invention attached to the fuel linesthereof.

Figure 2 is a longitudinal section and partial elevation of one of theheating units, and

Figure 3 is a cross-section of the device shown in Figure 2.

A Diesel engine of conventional design is represented at in Figure 1. Afuel pump ll, driven by the cam shaft or any suitable means, i providedwith four outlets l2, l3, l4 and I5, delivering fuel under pressurethrough lines l6, I1, I8 and I9 to injector assemblies 26, 2|, 22 and23, respectively, associated with the four cylinders of the engine.Since the details of the fuel pump, the injector assemblies and themeans for timing the injection of fuel into the cylinders form no partof the present invention, they will not be described herein.

The fuel lines I 6-! 9 are provided, in accordance with the invention,with heating devices 2 3, 25, 26 and 2?, respectively, each of which ispreferably positioned immediately ahead of the associated injectorassembly.

Since all of the heating units are of substantially the sameconstruction, only one need be described in detail. Referring to Figure2, the fuel line IS, in accordance with conventional design, comprises acopper or copper alloy pipe leading to a coupling 30 associated with theinjector head 20. A layer 3| of mica or equivalent material is wrappedaround the pipe l6 for a suitable length, thereby providing anelectrically insulating, heat resisting layer of good heat conductinmaterial. An electrical resistance element in the form of a metallicribbon 32 is wrapped in a spiral coil around the mica layer 3|, with oneof its ends 33 secured, as by a weld 34, in electrical contact with thepipe l6 and with its other end 35 projecting outwardly and provided witha terminal connection 36.

A second layer 31 of mica or equivalent material is wrapped around theresistance element, to maintain the convolutions thereof inpredetermined position and to insulate the ribbon from the outside.

Finally, a body 38 of heat insulating material covers the entireassembly, with the exception of the terminal connection 36. This body ispreferably formed of an asbestos cement composition and is moulded aboutthe mica layers and the resistance element, to seal them from externalatmosphere. Preferably, the heat insulating body 38 is sealed at itsends to the pipe I 6. Hence, substantially all of the heat generated bthe resistance element is concentrated and is directed inwardly, toraise the temperature of the pipe l6 and the fuel maintained underpressure therein.

As indicated in Figure 1, the several heating units may be energized bya battery 4i! having one lead 4! grounded to the engine at 42 and theother lead 43 connected, through a circuit breaker 44, to branch lines45, 45, 4'1, and 48, leading, respectively, to the terminals 36. of theresistance element 32. The current flows from the, battery 40 throughline 43, switch 44,. branch lines 45-48 and resistance elements 32 andre.- turns through the welded connections 34, fuel pipes 16-49,connection 42 and wire 4|. The invention contemplates the us of athermostat controlled switch, in addition to or as a substitute for themanually operated switch 44, so that the circuit will be automaticallyopened and the heating elements deenergized. after the engine has beenoperating for a suificient time to raise its temperature to apredetermined degree. In such case, the heating elements may beinitially energized by manual operation of a suitable switch andautomatically deenergized b a thermostat controlled device.

It is thought that the operation of the apparatus of the presentinvention will be apparent from the foregoing description. When it isdesired to start a cold engine equipped with the devices describedabove, it is simply necessary to complete the circuit to the severalheating elements, so that the fuel in the lines leading to the injectorassemblies is rapidly heated. The engine may then be turned over by theusual means, whereupon it will start immediately, as a result of theinjection of the hot fuel under high pressure into the air in thecylinder, which has been heated as a result of its compression by theengine piston. After the engine has operated for a short time, the partswill become suiiiciently heated to maintain normal operation of theengine, whereupon the heating devices may be electrically disconnected.

Although the invjention has been described with considerableparticularity in this specification, it must be understood that it isnot limited to the details of construction described above and shown inthe accompanying drawing, but includes all modifications coming withinthe scope of the appended claims and their equivalents.

I claim:

1. The combination with an engine of the Diesel type having a fuelinjector associated with its cylinder, a fuel pump and a pipe fordelivering fuel under pressure from the pump to the injector, of meansfor heating the fuel in said pipe, for starting purposes, to an elevatedtemperature below the point of vaporization of the fuel at the pressuremaintained in the pipe, said means comprising an electric resistanceelement positioned exteriorly of the pipe in heat exchange relationthereto, and means for conducting current therethrough, to heat theelement, the pipe and the fuel therein.

2. The combination with an engine of the Diesel type having a fuelinjector associated with its cylinder, a fuel pump and a pipe fordelivering fuel under pressure from the pump to the injector, of meanspositioned adjacent the injector for heating the fuel in said pipe, forstarting purposes, to an elevated temperature below the point ofvaporization of the fuel at the pressure maintained in the pipe, saidmeans comprising an elongated electric resistance element wound aroundthe pipe in heat exchange relation thereto and electrically insulatedtherefrom except at one end, said end being connected to the pipe, andmeans for conducting current through the element and for return throughthe pipe, to heat the element, the pipe and the fuel therein.

3. The combination with an engine of the Diesel type having a fuelinjector associated with its cylinder, a fuel pump and a pipe fordelivering fuel under pressure from the pump to the injector, of meanspositioned adjacent the injector for heating the fuel in said. pipe, forstarting purposes, to an elevated temperature below the point ofvaporization of the fuel at the pressure maintained in the pipe, saidmeans comprising a layer of heat conducting and electrically insulatingsheet material covering a portion of the pipe, an electric resistanceelement disposed exteriorly of said layer, a covering of heat insulatingmaterial surrounding the resistance element, and means for conductingcurrent through the element, whereby the heat generated thereby istransmitted through the first-mentioned layer to the pipe and the fueltherein.

4. The combination with an engine of the Diesel type having a fuelinjector associated with its cylinder, a fuel pump and a pipe fordelivering fuel under pressure from the pump to the injector, of meanspositioned adjacent the injector for heating the fuel in said pipe, forstarting purposes, to an elevated temperature below the point ofvaporization of the fuel at the pressure maintained in the pipe, saidmeans comprising a layer of heat conducting and electrically insulatingmaterial surrounding a portion of the pipe, an electric resistanceelement wrapped spirally around the layer and connected at one end tothe pipe, a covering of dielectric heat insulating material surroundingthe resistance element and in contact therewith, and means forconducting current through the resistance element for return through thepipe, thereby to heat the element, the pipe and the fuel therein.

5. A heater for the fuel line of a Diesel engine, positioned between thefuel pump and the fuel injector and adjacent the injector to heat thefuel in the line to facilitate starting, said heater comprising a layerof dielectric material of good heat transmitting character surroundingthe line ahead of and adjacent the injector assembly, an electricresistance element disposed in heat exchange relation upon the layer, abody of dielectric heat insulating material covering the element and thefirst-mentioned layer and substantially sealed at its ends to the line,whereby the heat from the resistance element is directed inwardly toraise the temperature of the line and the fuel therein, and anelectrical connection disposed exteriorly of said body and leading tosaid element.

6. A heater for the fuel line of a Diesel engine, positioned between thefuel pump and the fuel injector, to heat the fuel in the line tofacilitate starting, said heater comprising a layer of resistant, heattransmitting, electrically insulating sheet material surrounding theline directly ahead of the injector assembly, an electric resistanceelement coiled about the layer in heat exchange relation thereto andhaving one of its ends connected to the line and its other endprojecting outwardly therefrom, another layer of resistant electricallyinsulating material covering the resistance element, and a body of heatinsulating material covering the last-mentioned layer, but exposing theoutwardly projecting end of the resistance element for connection to asource of current, said body serving to direct the heat from theresistance element inwardly to raise the temperature of the line and thefuel therein.

7. A heater for the fuel line of a Diesel engine, positioned between thefuel pump and the fuel injector, to heat the fuel in the line tofacilitate starting, said heater comprising a layer of mica surroundingthe line ahead of the injector assembly, an electric resistance elementcoiled about the layer in heat exchange relation thereto and having oneof its ends connected to the line and its other end projecting outwardlytherefrom, another layer of mica covering the resistance element, and abody of asbestos-cement composition covering the last-mentioned layerand sealed at its ends to the outer surface of said line, but exposingthe outwardly projecting end of the resistance element for connection toa source of current, said body serving to direct the heat from theresistance element inwardly to raise the temperature of the line and thefuel therein.

JAMES D. PULLIAM.

